As an insult, its target domain is broad, and can extend to anyone engaged in a public show of secular humanism or anyone in the insulter's eye seen to be wielding science as a weapon against their religion, though given the wild overuse of the term Bible thumper, this might well be merely analogous.

Perhaps "atheist Thumper" describes a famous bunny rabbit after his friend Bambi was shot. Seeing all the pain and suffering in the world, highlighted by the deer's demise, said rabbit went on to ponder at great length the problem of evil. However, this statement is unfortunately unsupported by any real "facts".